Electric generation control system for hybrid vehicle

ABSTRACT

When a target generated output established for a generator by a target generated output setting unit depending on an operating condition of a hybrid vehicle varies, an intake air control valve control unit starts varying the opening of an intake air control valve of an engine in order to equalize the power output of the engine to a new varied target generated output. A delay time estimating unit estimates a delay time after the opening of the intake air control valve has started to vary until the engine eventually produces a power output corresponding to the new target generated output according to a preset correlation based on the present rotational speed of the engine. Upon elapse of the estimated delay time after the opening of the intake air control valve has started to vary, a generator controller increases or reduces the generated output of the generator into agreement with the target generated output. At the time the generated output of the generator is controlled, the power output of the engine matches the generated output of the generator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric generation control systemfor use on a hybrid vehicle having a propulsive electric motorenergizable by a battery and an electric generator actuated by aninternal combustion engine for energizing the propulsive electric motor.

2. Description of the Related Art

Growing concern in recent years over environmental protection has led tovarious efforts to develop for practical applications electric vehicleswhich have a propulsive electric motor energizable by a battery totransmit drive forces to drive wheels for propelling the electricvehicle. One of the important requirements for such electric vehicles tosatisfy is that the range which they can travel without recharging thebattery be maximized and the discharging of the battery be minimized forincreased battery service life.

One solution disclosed in Japanese laid-open patent publication No.3-169203 is a hybrid vehicle carrying an electric energy generatingapparatus having an electric generator and an internal combustion enginefor actuating the electric generator. Electric energy generated by theelectric generator is supplied to charge a battery or to energize apropulsive electric motor.

While the disclosed hybrid vehicle is running, the battery energizes theelectric generator to operate as an electric motor in a motor mode tostart the engine. After the engine has been started, the electricgenerator is switched from the motor mode to a generator mode in whichit is actuated by the engine to generate electric energy, and then theengine is warmed up. Thereafter, the electric generator is operated togenerate an appropriate amount of electric energy depending on anoperating condition of the hybrid vehicle, such as the vehicle speed ofthe hybrid vehicle, and the generated electric energy is supplied to thebattery or the propulsive electric motor.

The electric generator is operated to generate the electric energy asfollows: Depending on an operating condition of the hybrid vehicle, suchas the vehicle speed of the hybrid vehicle, a target generated outputfor the electric generator is obtained from a predetermined data tableor the like. Then, the engine is controlled to produce a power output(drive forces to actuate the electric generator) which corresponds tothe target generated output. The engine is controlled by regulating,with an actuator or the like, the opening of a throttle valve (intakeair control valve) of the engine into a throttle valve openingcorresponding to the target generated output. The generated output ofthe electric generator is also increased or reduced into agreement withthe target generated output by controlling an output current from theelectric generator with an inverter circuit or the like. The abovegenerator control process is carried out from time to time to cause theelectric generator to generate an amount of electric energy depending onthe operating condition of the hybrid vehicle.

In the above generator control process, once the target generated outputis determined, the electric energy generated by the electric generatorcan be controlled substantially on a real-time basis according to thetarget generated output. Therefore, the electric energy generated by theelectric generator can be controlled to catch up with the targetgenerated output even when the target generated output varies from timeto time. However, after the target generated output has been determined,the power output control of the engine tends to suffer a delay, from theelectric energy control of the electric generator, until the engineproduces a power output corresponding to the target generated output.Specifically, the power output control of the engine is carried out bymechanically moving the throttle valve with the actuator to control theopening of the throttle valve. When the target generated output varies,the actuator starts actuating the throttle valve to control its openingto cause the engine to produce a mechanical power output correspondingto the target generated output which has varied, but a certain time isrequired before the opening of the throttle valve eventually reaches anopening corresponding to the target generated output. Even after theopening of the throttle valve has eventually reached an openingcorresponding to the target generated output, a certain time is furtherrequired until the amount of intake air introduced into the enginereaches an amount corresponding to the target generated output.Consequently, when the target generated output varies, if the electricenergy control of the electric generator and the power output control ofthe engine start to be effected simultaneously according to the targetgenerated output which has varied, then the electric energy generated bythe electric generator is immediately controlled, but there is a delaytime until the actual power output of the engine reaches a power outputcorresponding to target generated output which has varied. With such adelay time, the electric energy generated by the electric generator isinappropriate with respect to the actual power output of the engineafter the power output control of the engine is effected until theactual power output of the engine reaches a power output correspondingto target generated output which has varied. As a result, the enginesuffers an unwanted load variation, and tends to operate unstably. Forexample, when the target generated output is increased, the electricgenerator is immediately electrically controlled to increase itsgenerated output, but the engine requires a certain period of time untilits power output reaches a power output commensurate with the generatedoutput of the electric generator. During such a certain period of time,the electric generator generates an electric energy output higher thanthe electric energy output that matches the actual power output of theengine. Therefore, the engine suffers an excessive load, and operatesunstably.

If the operation of the engine becomes unstable, then the engine iscaused to emit unwanted harmful exhaust gases or vibrate undesirably.

The delay time of the engine control at the time the target generatedoutput varies differs with the rotational speed of the engine and alsodiffers depending on a change in the rotational speed of the enginewhich is caused by the variation in the target generated output andwhether the rotational speed of the engine increases or decreases due tothe variation in the target generated output.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide anelectric generation control system for use on a hybrid vehicle which iscapable of controlling the power output of an engine which actuates anelectric generator of electric energy generating apparatus on the hybridvehicle and the generated electric energy output of the electricgenerator with accurate timing for thereby reducing unwanted variationsin the load on the engine and preventing the engine from emittingundesirable exhaust gases and unduly vibrating.

To accomplish the above object, there is provided in accordance with thepresent invention an electric generation control system for use on ahybrid vehicle having a vehicle propelling apparatus including a batteryand a propulsive electric motor energizable by the battery, and anelectric energy generating apparatus including an engine and a generatoractuatable by the engine, the generator being operable in a generatormode in which the generator is actuated by the engine to generateelectric energy to be supplied to the battery and/or the propulsiveelectric motor while the vehicle propelling apparatus is in operation,the electric generation control system comprising target generatedoutput setting means for establishing a target generated output for thegenerator depending on an operating condition of the hybrid vehicle,intake air control valve control means for controlling the opening of anintake air control valve of the engine to enable the engine to produce apower output corresponding to the target generated output, generatorcontrol means for varying the electric energy generated by the generatorto equalize the generated electric energy to the target generatedoutput, and delay time estimating means for estimating a delay timeuntil the engine produces the power output corresponding to the targetgenerated output after the opening of the intake air control valvestarts being varied by the intake air control valve control meansdepending on a change in the target generated output, according to apreset correlation between delay times and rotational speeds of theengine based on a present rotational speed of the engine, the generatorcontrol means comprising means for controlling the electric energygenerated by the generator based on the target generated output uponelapse of the delay time after the opening of the intake air controlvalve starts being varied by the intake air control valve control means.

When the target generated output established by the target generatedoutput setting means depending on the operating condition of the hybridvehicle varies, the intake air control valve control means startsvarying the opening of the intake air control valve in order to equalizethe power output of the engine to a new varied target generated output.The delay time estimating means estimates a delay time after the openingof the intake air control valve has started to vary until the engineeventually produces the power output corresponding to the new targetgenerated output according to the preset correlation based on thepresent rotational speed of the engine. Upon elapse of the estimateddelay time after the opening of the intake air control valve has startedto vary, the generator control means increases or reduces the generatedoutput of the generator into agreement with the target generated output.At the time the generated output of the generator is controlled, thepower output of the engine matches the generated output of thegenerator. Therefore, the engine is subjected to an adequate load, anddoes not suffer undue load variations, so that the engine does notdischarge unwanted exhaust emissions or does no unduly vibrate.

Consequently, the generator generates electric energy while the poweroutput of the engine and the generated output of the generator actuatedby the engine are being synchronized with each other at accurate timing,thereby allowing the engine to operate stably. Since the engine operatesstably, it is prevented from emitting undesirable exhaust gases andunduly vibrating. Therefore, the hybrid vehicle has improved emissionand vibration performances.

The target generated output is determined depending on the vehicle speedof the hybrid vehicle. In this manner, the generator is caused toproduce a generated output commensurate with the amount of electricenergy consumed by the propulsive electric motor which corresponds tothe vehicle speed of the hybrid vehicle, and the generated output issupplied to the battery and the propulsive electric motor. Theconsumption by the propulsive electric motor of electric energy suppliedfrom the battery is now suppressed to an appropriate level.

Immediately after the engine and the generator have been started, thegenerator generates electric energy while the engine is being warmed upin order to prevent an excessive load from being imposed on the enginewhen the engine is not sufficiently warm. In the warm-up of the engine,a target generated output for the generator is determined depending onthe temperature of the engine. This permits the generator to generateelectric energy while the engine is being warmed up with the load on theengine being optimized for the warming-up operation of the engine. Afterthe engine has been warmed up, a target generated output is determineddepending on the vehicle speed of the hybrid vehicle. Therefore, thegenerator is caused to produce a generated output commensurate with theamount of electric energy that is consumed by the propulsive electricmotor.

When the intake air control valve is controlled by the intake aircontrol valve control means, a target rotational speed for the engine toproduce a power output from the engine corresponding to the targetgenerated output is determined, and the opening of the intake aircontrol valve is controlled to equalize the rotational speed of theengine to the target rotational speed. The engine is now controlled toproduce a power output corresponding to the target generated output forthe generator.

The electric generation control system further comprises rotationalspeed change calculating means for determining a change in therotational speed of the engine depending on a change in the targetgenerated output, and the delay time estimating means comprises meansfor estimating the delay time according to a preset correlation betweendelay times, rotational speeds of the engine, and changes in therotational speed based on the present rotational speed of the engine andthe determined change in the rotational speed. The delay time estimatingmeans estimates a delay time according to the preset correlation basedon the present rotational speed of the engine and the change in therotational speed thereof depending on the change in the target generatedoutput. The correlation is arranged such that the delay time is shorteras the rotational speed of the engine is higher and longer as the changein the rotational speed of the engine is larger.

The electric generation control system further comprises rotationalspeed increase/decrease determining means for determining whether therotational speed of the engine increases or decreases depending on thechange in the target rotational speed, the correlation being availableseparately when the rotational speed of the engine increases and whenthe rotational speed of the engine decreases. The correlation isarranged such that the delay time is shorter when the rotational speedof the engine increases than when the rotational speed of the enginedecreases.

As described above, the correlation for estimating a delay time isestablished depending on rotational speeds of the engine, and changes inthe rotational speed thereof due to changes in the target generatedoutput, and the correlation is available separately when the rotationalspeed of the engine increases and when the rotational speed of theengine decreases. With this arrangement, a delay time can accurately beestimated from the correlation. Inasmuch as a delay time can accuratelybe estimated, the control process of synchronizing the power output ofthe engine and the generated output of the generator in timedrelationship can be performed reliably and accurately.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description when takenin conjunction with the accompanying drawings which illustrate apreferred embodiment of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system arrangement of a hybrid vehicle towhich the present invention is applied;

FIG. 2 is a block diagram of a portion of an electric energy generatingapparatus of the hybrid vehicle shown in FIG. 1;

FIG. 3 is a block diagram of a portion of the electric energy generatingapparatus of the hybrid vehicle shown in FIG. 1;

FIG. 4 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates;

FIGS. 5 and 6 are flowcharts of an operation sequence of the electricenergy generating apparatus of the hybrid vehicle shown in FIG. 1;

FIG. 7 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates;

FIG. 8 is a flowchart of a cranking control mode of operation of theelectric energy generating apparatus of the hybrid vehicle shown in FIG.1;

FIG. 9 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe cranking control mode;

FIG. 10 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe cranking control mode;

FIG. 11 is a flowchart of a full-combustion decision mode of operationof the electric energy generating apparatus of the hybrid vehicle shownin FIG. 1;

FIG. 12 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe full-combustion decision mode;

FIG. 13 is a flowchart of a generator switching control mode ofoperation of the electric energy generating apparatus of the hybridvehicle shown in FIG. 1;

FIGS. 14(a) and 14(b) are diagrams showing the manner in which theelectric energy generating apparatus of the hybrid vehicle shown in FIG.1 operates in the generator switching control mode;

FIG. 15 is a flowchart of a warm-up control mode of operation of theelectric energy generating apparatus of the hybrid vehicle shown in FIG.1;

FIG. 16 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe warm-up control mode;

FIG. 17 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe warm-up control mode;

FIG. 18 is a flowchart of an electric generation control mode ofoperation of the electric energy generating apparatus of the hybridvehicle shown in FIG. 1;

FIG. 19 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe electric generation control mode;

FIG. 20 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe electric generation control mode;

FIG. 21 is a flowchart of a regeneration control mode of operation ofthe electric energy generating apparatus of the hybrid vehicle shown inFIG. 1;

FIG. 22 is a diagram showing the manner in which the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1 operates inthe regeneration control mode; and

FIG. 23 is a flowchart of an operation sequence of the electric energygenerating apparatus of the hybrid vehicle shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the system arrangement of a hybrid vehicle to whichthe present invention is applied generally includes a vehicle propellingapparatus 1 and an electric energy generating apparatus 2.

The vehicle propelling apparatus 1 comprises a battery 3, a propulsiveelectric motor 4 energizable by the battery 3, a motor energy supplycontroller 5 including an inverter circuit, etc. (not shown) forcontrolling the supply of electric energy between the battery 3 and thepropulsive electric motor 4, a vehicle propulsion management device 6for controlling the propulsive electric motor 4 through the motor energysupply controller 5 and recognizing the remaining capacity of thebattery 3, an accelerator operation sensor 7 for detecting anaccelerator operation A carried out by the driver of the hybrid vehicle,a brake switch 8 for detecting whether the driver has applied a brakingaction or not, a vehicle speed sensor 9 for detecting a vehicle speedV_(CAR), a current sensor 10a for detecting a discharged current and acharged current (hereinafter referred to as a "battery current I_(B) ")of the battery 3, a current sensor 10b for detecting a current(hereinafter referred to as a "motor current I_(M) ") of the propulsiveelectric motor 4, and a voltage sensor 11 for detecting a voltage(hereinafter referred to as a "battery voltage V_(B) ") across thebattery 3.

The vehicle propulsion management device 6 comprises a microcomputer orthe like, and is programmed to perform various functions which include,as shown in FIG. 2, a motor control unit 12 for controlling thepropulsive electric motor 4 through the motor energy supply controller 5based on detected signals from the accelerator operation sensor 7, thebrake switch 8, and the vehicle speed sensor 9, a remaining capacityrecognizing unit 13 for recognizing the remaining capacity of thebattery 3 based on detected signals from the current sensor 10a and thevoltage sensor 11, a current/voltage characteristics detecting unit 14for detecting present current/voltage characteristics of the battery 3based on detected signals from the current sensor 10a and the voltagesensor 11, and an effective maximum output calculating unit 15 fordetermining an effective maximum output that can be produced by thebattery 3 at a predetermined minimum drive voltage from the presentcurrent/voltage characteristics of the battery 3 which are detected bythe current/voltage characteristics detecting unit 14.

Basically, the motor control unit 12 determines a target torque for thepropulsive electric motor 4 according to a preset map or the like basedon the accelerator operation A and the vehicle speed V_(CAR) which aredetected by the accelerator operation sensor 7 and the vehicle speedsensor 9, and imparts the determined target torque to the motor energysupply controller 5. The motor energy supply controller 5 controls thesupply of electric energy from the batter 3 to the propulsive electricmotor 4 with switching pulses in order to enable the propulsive electricmotor 4 to produced the given target torque.

When the accelerator operation A detected by the accelerator operationsensor 7 is reduced or an ON signal (hereinafter referred to as a"braking signal BR") indicative of a braking action is supplied from thebrake switch 8 while the hybrid vehicle is running, the motor controlunit 12 instructs the motor energy supply controller 5 to effectregenerative braking on the propulsive electric motor 4. At this time,the motor energy supply controller 5 supplies a regenerated current fromthe propulsive electric motor 4 to the battery 3, thereby charging thebattery 3. The regenerated current from the propulsive electric motor 4is detected by the current sensor 10b as a motor current I_(M) thatflows from the motor energy supply controller 5 to the battery 3.

Basically, the remaining capacity recognizing unit 13 integrates theproduct of the battery current I_(B) and the battery voltages V_(B),i.e., the electric energy, which are detected respectively by thecurrent sensor 10 and the voltage sensor 11 at each sampling time forthereby determining discharged and charged amounts of electric energy ofthe battery 3, and subtracts the discharged amount of electric energyfrom and adds the charged amount of electric energy to the initialcapacity of the battery 3 for thereby recognizing the remaining capacityC of the battery 3 from time to time.

The current/voltage characteristics detecting unit 14 stores a pluralityof sets of the battery current I_(B) and the battery voltages V_(B)detected at respective sampling times in a memory (not shown) within apredetermined period of time that is longer than the sampling times.Then, as shown in FIG. 4, the current/voltage characteristics detectingunit 14 determines a linear characteristic curve "a" representing thepresent current/voltage characteristics of the battery 3 from the storedsets of the battery current I_(B) and the battery voltages V_(B)according to the method of least squares or the like.

The effective maximum output calculating unit 15 determines, from thelinear characteristic curve "a", a current I₁ at a minimum drive voltageV₁ (see FIG. 4) required to drive the propulsive electric motor 4, i.e.,a current I₁ that is discharged by the battery 3 when the voltage acrossthe battery 3 is the minimum drive voltage V₁. Then, the effectivemaximum output calculating unit 15 determines the product V of thecurrent I₁ and the minimum drive voltage V₁ as an effective maximumoutput P_(MAX) which is indicated as a hatched area in FIG. 4. When theremaining capacity C of the battery 3 is reduced, the linearcharacteristic curve "a" moves downwardly as indicated by a hypotheticalcurve "a'" in FIG. 4. Therefore, the effective maximum output P_(MAX) isreduced as the remaining capacity C of the battery 3 is lowered.

The remaining capacity C of the battery 3, the effective maximum outputP_(MAX), the vehicle speed V_(CAR) detected by the vehicle speed sensor9, the accelerator operation A detected by the accelerator operationsensor 7, the braking signal BR from the brake switch 8, and the motorcurrent I_(M) detected by the current sensor 10b are supplied to anelectric generation management device (described below) of the electricenergy generating apparatus 2.

Drive forces generated by the propulsive electric motor 4 aretransmitted through a power transmitting system (not shown) to drivewheels of the hybrid vehicle, thereby propelling the hybrid device.

In FIG. 1, the electric energy generating apparatus 2 comprises aninternal combustion engine 16, an electric generator 17 which can beactuated by the engine 16, an engine controller 18 for controlling theengine 16 and auxiliary components (described later) combined therewith,a generator energy supply controller 19 including an inverter circuit(not shown), etc. for controlling the supply of electric energy betweenthe battery 3 and the propulsive electric motor 4 or the generator 17, agenerator controller 20 for controlling the generator 17 through thegenerator energy supply controller 19, an electric generation managementdevice 21 for managing and controlling the electric energy generatingapparatus 2 through the engine controller 18 and the generatorcontroller 20, and an atmospheric pressure sensor 22 for detecting anatmospheric pressure At_(P).

The generator 17 has a rotor (not shown) coupled to the crankshaft (notshown) of the engine 16 so that the rotor will rotate at the same speedas the crankshaft.

The engine 16 is combined with auxiliary components which include anexhaust gas sensor 23, an exhaust gas purifying catalyst 24, atemperature sensor 25 for detecting a temperature T_(W) of the engine16, i.e., a coolant temperature, a load detector 26 for detecting a loadL on the engine 16, i.e., a load torque on the crankshaft of the engine16, a engine speed sensor 27 for detecting a rotational speed of theengine 16, i.e., a rotational speed of the generator 17, a throttleactuator 28 for actuating a throttle valve (not shown) of the engine 16,a fuel supply device 29 for supplying fuel to the engine 16, and acanister purging system 30 for purging a canister (not shown) associatedwith the fuel supply device 29. The exhaust gas purifying catalyst 24comprises a catalyst which can be activated when it is heated by anelectric current supplied thereto. When the canister needs to be purged,the canister purging system 30 applies a canister purge request signalto the engine controller 18, through which the purge request signal issupplied to the electric generation management device 21. The canisteris purged to lower the vapor pressure of a fuel gas that is stored inthe canister for thereby improving the exhaust gas emission performanceof the engine 16. The canister is purged when the engine 16 istemporarily in operation.

The electric generation management device 21, the engine controller 18,and the generator controller 20 comprise a microcomputer or the like,and are programmed to perform various functions described below.

As shown in FIG. 3, the electric generation management device 21comprises a start commanding unit 31 for issuing a start signal to theengine controller 18 and the generator controller 20 to activate theelectric energy generating apparatus 2, a cranking commanding unit 32for cranking the engine 16 to start through the engine controller 18 andthe generator controller 20, an ignition commanding unit 33 for ignitingfuel in the engine 16 through the engine controller 18 when the engine16 is cranked, a switching commanding unit 34 for switching thegenerator 17 from a motor mode in which it operates as a starter motorto crank the engine 16 to a generator mode in which the generator 17operates as a generator, through the generator controller 20, anelectric generation control unit 36 for controlling electric generationby the engine 16 after it has been started and the generator 17 andwarm-up operation of the engine 16 through the engine controller 18 andthe generator controller 20, and a regeneration control unit 37 forcontrolling electric generation by the engine 16 and the generator 17through the electric generation control unit 36 upon regenerativebraking on the propulsive electric motor 4. The start commanding unit 31has a threshold value setting unit 31a for establishing a thresholdvalue for the remaining capacity C of the battery 3 which determines thetiming to start the electric energy generation apparatus 2. The crankingcommanding unit 32 has a starting rotational speed setting unit 32a forestablishing a starting rotational speed for the engine 16, i.e., astarting rotational speed for the generator 17, when the engine 16 iscranked. The electric generation control unit 36 comprises a targetgenerated output setting unit 36a (target generated output settingmeans) and a target rotational speed setting unit 36b for establishing atarget generated output and a target rotational speed, respectively, forthe generator 17 depending on the vehicle speed V_(CAR) upon electricgeneration by the generator 17, a rotational speed change calculatingunit 36c (rotational speed change calculating means) for determining atime-dependent change in the target rotational speed established by thetarget rotational speed setting unit 36b, a rotational speedincrease/decrease determining unit 36d (rotational speedincrease/decrease determining means) for determining whether therotational speed of the engine 16 (=the rotational speed of thegenerator 17) increases or decreases depending on whether the change inthe target rotational speed determined by the rotational speed changecalculating unit 36c is positive or negative, and a delay timeestimating unit 36e (delay time estimating means) for estimating a delaytime (described later on) depending on the rotational speed N of theengine 16 detected by the engine speed sensor 27, the time-dependentchange in the target rotational speed, and whether the rotational speedof the engine 16 increases or decreases.

The electric generation management device 21 is supplied with variousdetected signals, including a detected signal indicative of theremaining capacity C of the battery 3, from the vehicle propulsionmanagement device 6, and also a detected signal from the atmosphericpressure sensor 22. The electric generation management device 21 isfurther supplied with detected signals from the temperature sensor 25and the engine speed sensor 27. Based on the supplied signals, theelectric generation management device 21 manages and controls theelectric energy generation apparatus 2 as described in detail later on.

The engine controller 18 comprises a sensor/catalyst energizing unit 38for energizing and activating the exhaust gas sensor 23 and the exhaustgas purifying catalyst 24 based on a start signal issued from the startcommanding unit 31, an activation determining unit 39 for determiningwhether the exhaust gas sensor 23 and the exhaust gas purifying catalyst24 have been activated or not and imparting a determined signal to theelectric generation management device 21, a starting ignition controlunit 40 for controlling the ignition of fuel in the engine 16 upon startof the engine 16 through the fuel supply device 29 and an ignitiondevice (not shown) based on an ignition command from the ignitioncommanding unit 33, a full-combustion determining unit 41 fordetermining whether the combustion of fuel in the engine 16 has reacheda fully combusted state when the engine 16 is ignited, and imparting adetermined signal to the electric generation management device 21, acombustion control unit 42 for controlling the combustion of fuel in theengine 16 through the fuel supply device 29 based on a command signalfrom the electric generation control unit 36, and a throttle controlunit 43 for controlling the opening of throttle valves of the engine 16through the throttle actuator 28 based on command signals from thecranking commanding unit 32 and the electric generation control unit 36when the engine 16 is cranked, warming up, or subsequently operated.

The engine controller 18 is supplied with command signals from theelectric generation management device 21 and detected signals from theexhaust gas sensor 23, the temperature sensor 25, the load detector 26,and the engine speed sensor 27. Based on the supplied signals, theengine controller 18 controls the engine 16 as described in detail lateron.

The generator controller 20 comprises a motor control unit 44 foroperating the generator 17 as a starter motor for the engine 16 throughthe generator energy supply controller 19 based on a command signal fromthe cranking commanding unit 32, a switching control unit 45 forswitching the generator 17 from the motor mode to the generator modethrough the generator energy supply controller 19 based on a commandsignal from the switching commanding unit 34, and a generator controlunit 46 for controlling electric generation by the generator 17 throughthe generator energy supply controller 19 based on a command signal fromthe electric generation control unit 36.

The generator controller 20 is supplied with a detected signal from theengine speed sensor 27 through the engine controller 18 as well ascommand signals from the electric generation management device 21. Basedon the supplied signals, the generator controller 20 controls thegenerator 17 through the generator energy supply controller 19 asdescribed in detail later on.

The electric generation control unit 36 of the electric generationmanagement device 21, the throttle control unit 43 of the enginecontroller 18, and the throttle actuator 28 jointly serve as intake aircontrol valve control means 47. The electric generation control unit 36of the electric generation management device 21, the generator controlunit 46 and the generator energy supply controller 19 of the generatorcontroller 20 jointly serve as generator control means 48.

Operation of the electric energy generating apparatus 2 of the hybridvehicle will be described below.

While the vehicle propelling apparatus 1 is in operation, e.g., whilethe hybrid vehicle is running or temporarily stopping, the electricgeneration management device 21 carries out a routine shown in FIGS. 5and 6 in every cycle time of 10 milliseconds., for example.

As shown in FIG. 5, the electric generation management device 21 firststarts a 10-ms. timer in a STEP 1, and then the threshold value settingunit 31a establishes a threshold value C_(L) for the remaining capacityC of the battery 3 in a STEP 2. The threshold value C_(L) is used todetermine whether the electric energy generating apparatus 2 is to beactivated or not. Specifically, the threshold value setting unit 31aestablishes the threshold value C_(L) according to a predetermined datatable as shown in FIG. 7 depending on the present atmospheric pressureAt_(P) detected by the atmospheric pressure sensor 22. As shown in FIG.7, the threshold value C_(L) is higher as the detected atmosphericpressure At_(P) is lower. Under the atmospheric pressure in a plaingeographic region, the threshold value C_(L) is set to 20% of the fullbattery capacity which is 100% when the battery 3 is fully charged. In ahighland where the atmospheric pressure is lower than the atmosphericpressure in a plain geographic region, the threshold value C_(L) is setto a value higher than 20%, e.g., 40% of the full battery capacity.

After having established the threshold value C_(L), the electricgeneration management device 21 carries out decision STEPs 3˜10, andactivates the engine controller 18 depending on the results of thedecision STEPs 3˜10.

Specifically, the electric generation management device 21 determineswhether an E.M.Flg (Energy Management Flag) is "1" or "0" in a STEP 3.The E.M.Flg indicates whether a electric energy generation control mode(described later on) has been carried out or not. The E.M.Flg is "1" ifthe electric energy generation control mode has been carried out, and"0" if the electric energy generation control mode has not been carriedout. If the E.M.Flg is "1" in the STEP 3 (YES), then the electric energygeneration control mode is continuously carried out.

If the E.M.Flg is "0" in the STEP 3 (NO), then the electric generationmanagement device 21 determines whether the canister is being purged ornot in a STEP 4. If the canister is being purged (at this time, theengine 16 is controlled by the engine controller 18 under the commandfrom the canister purging system 30), then electric generationmanagement device 21 resets the E.M.Flg to "0" in a STEP 12, andthereafter suspends or inactivates the electric energy generatingapparatus 2 in a STEP 13. Specifically in the STEP 13, the supply ofelectric energy from the generator 17 to the battery 3 and thepropulsive electric motor 4 is stopped or suspended, but the engine 16is controlled by the canister purging system 30.

If the canister is not being purged in the STEP 4 (NO), then theelectric generation management device 21 compares the present remainingcapacity C of the battery 3 which is recognized by the remainingcapacity recognizing unit 13 with the established threshold value C_(L)in a STEP 5. If C≧C_(L), i.e., if the remaining capacity C of thebattery 3 is not substantially lowered, then the electric generationmanagement device 21 compares the present effective maximum outputP_(MAX) of the battery 3 which is determined by the effective maximumoutput calculating unit 15 with a predetermined required maximum outputP_(motor) for the propulsive electric motor 4, i.e., a power output ofthe propulsive electric motor 4 which is required when the acceleratoroperation A is maximum, in a STEP 6.

If C<C_(L) or P_(MAX) ≧P_(motor), i.e., if remaining capacity C of thebattery 3 is substantially lowered or the battery 3 is incapable ofproducing an energy output necessary to propel the hybrid vehicle, thenthe start commanding unit 31 of the electric generation managementdevice 21 applies start signals successively to the engine controller 18and the generator controller 20 to activate them in STEPs 8, 8a, 9, 9a.When the engine controller 18 is activated, the sensor/catalystenergizing unit 38 starts energizing and activating the exhaust gassensor 23 and the exhaust gas purifying catalyst 24, and simultaneouslythe activation determining unit 39 starts determining whether theexhaust gas sensor 23 and the exhaust gas purifying catalyst 24 havebeen activated or not. Specifically, the activation determining unit 39determines whether the exhaust gas sensor 23 and the exhaust gaspurifying catalyst 24 have been energized by the sensor/catalystenergizing unit 38 for respective periods of time in excess of presetperiods of time, or the temperatures of the exhaust gas sensor 23 andthe exhaust gas purifying catalyst 24 have exceeded respective presettemperatures. When the exhaust gas sensor 23 and the exhaust gaspurifying catalyst 24 have been energized for respective periods of timein excess of preset periods of time, or the temperatures of the exhaustgas sensor 23 and the exhaust gas purifying catalyst 24 have exceededrespective preset temperatures, the activation determining unit 39determines that both the exhaust gas sensor 23 and the exhaust gaspurifying catalyst 24 have been activated, and outputs a signalindicative of their activation to the electric generation managementdevice 21.

After having activated the engine controller 18 and the generatorcontroller 20, the electric generation management device 21 instructsthe engine controller 18 to effect an initial control process foroperating the engine 16 in STEPs 10, 10a. After the initial controlprocess, the electric generation management device 21 determines whetherthe exhaust gas sensor 23 and the exhaust gas purifying catalyst 24 havebeen activated or not based on a signal from activation determining unit39 in a STEP 11.

If C≧C_(L) and P_(MAX) >P_(motor) in the STEPs 5, 6, i.e., if thebattery 3 has a sufficient remaining capacity, then the electricgeneration management device 21 determines whether there is a canisterpurge request signal from the canister purging system 30 or not in aSTEP 7. If there is no canister purge request signal, then the electricenergy generating apparatus 2 is suspended or inactivated in the STEPs12, 13. If there is a canister purge request signal from the canisterpurging system 30 in the STEP 7 (YES), then the electric generationmanagement device 21 activates the engine controller 18 for enabling thecanister purging system 30 to purge the canister.

As described above, if the remaining capacity C of the battery 3 issubstantially lowered (C<C_(L)) or the battery 3 is incapable ofproducing an energy output necessary to propel the hybrid vehicle(P_(MAX) ≦P_(motor)) while the vehicle propelling apparatus 1 is inoperation, then except when the canister is being purged, the enginecontroller 18 and the generator controller 20 are activated by the startcommanding unit 31 of the electric generation management device 21, andthe exhaust gas sensor 23 and the exhaust gas purifying catalyst 24 areenergized and activated by the sensor/catalyst energizing unit 38.

Because the threshold value C_(L) for remaining capacity C of thebattery 3 is greater as the ambient atmospheric pressure AT_(P) islower, the engine controller 18 is activated earlier in a highland wherethe atmospheric pressure AT_(P) is relatively low than in a plaingeometrical region.

If the exhaust gas sensor 23 and the exhaust gas purifying catalyst 24have been activated as confirmed by a signal from activation determiningunit 39 in the STEP 11 (YES), the electric generation management device21 determines whether the difference |N_(CR) -N| between a startingrotational speed N_(CR) (cranking rotational speed N_(CR)) establishedby the starting rotational speed setting unit 32a for the engine 16 anda present rotational speed N (=a rotational speed of the generator 17)of the engine 16 detected by the engine speed sensor 27 is smaller thana predetermined value ΔN or not, i.e., if the present rotational speed Nof the engine 16 substantially agrees with the starting rotational speedN_(CR) or not, in a STEP 14 (see FIG. 6). If |N_(CR) -N|≧ΔN, i.e., ifthe engine 16 and the generator 17 are inactivated or the engine 16 hasjust begun to be cranked, then the cranking commanding unit 32 issues acranking command to the generator controller 20 to crank the engine 16in a STEP 15, and carries out a cranking control mode in which theengine 16 is cranked by the generator 17 as a starter motor in a STEP16.

The cranking control mode in the STEP 16 is effected by the crankingcommanding unit 32 as shown in FIG. 8.

In the cranking control mode shown in FIG. 8, the starting rotationalspeed setting unit 32a of the cranking commanding unit 32 determines atarget starting rotational speed N_(CR) from a data table shown in FIG.9 based on a present engine temperature T_(W) of the engine 16 which isdetected by the temperature sensor 25, and determines a target throttleopening TH_(CR) for the engine 16 from a data table shown in FIG. 10 ina STEP 1. The data tables shown in FIGS. 9 and 10 contain predetermineddifferent target starting rotational speeds N_(CR) and predetermineddifferent target throttle openings TH_(CR), respectively, correspondingto various engine temperatures T_(W) of the engine 16 for better exhaustgas characteristics of the engine 16.

The cranking commanding unit 32 outputs the determined target startingrotational speed N_(CR) and the determined target throttle openingTH_(CR) respectively to the generator controller 20 and the enginecontroller 18 in respective STEPs 2, 3.

At this time, the motor control unit 44 of the generator controller 20determines, according to a given formula, a command value for a motorcurrent necessary to bring the present rotational speed N of thegenerator 17 (=the rotational speed of the engine 16) into agreementwith the target starting rotational speed N_(CR) when the generator 17operates as an electric motor, and gives the determined command value tothe generator energy supply controller 19. Based on the given commandvalue, the generator energy supply controller 19 adjusts the duty cycleof switching pulses for controlling the electric energy supplied fromthe battery 3 to the generator 17. In this manner, the electric energysupplied from the battery 3 to the generator 17 which operates as anelectric motor is controlled by a feedback loop until the rotationalspeed N of the generator 17 agrees with the target starting rotationalspeed N_(CR).

The throttle control unit 43 of the engine controller 18 controls thethrottle opening of the engine 16 through the throttle actuator 28 untilthe throttle opening of the engine 16 agrees with the target throttleopening TH_(CR).

If |N_(CR) -N|<ΔN in the STEP 14 (YES) as a result of the crankingcontrol mode shown in FIG. 8, i.e., if the rotational speed N of thegenerator 17 substantially agrees with the target starting rotationalspeed N_(CR), then the electric generation management device 21determines whether the combustion of fuel in the engine 16 has reached afully combusted state or not based on a signal issued from thefull-combustion determining unit 41 in a STEP 17. If not, the electricgeneration management device 21 imparts an ignition command to theengine controller 18 to ignite fuel in the engine 16 in a STEP 18.

At this time, the starting ignition control unit 40 controls the fuelsupply unit 29 to start supplying fuel to the engine 16, and alsocontrols the non-illustrated ignition device to ignite fuel in theengine 16, starting to combust fuel in the engine 16. The startingignition control unit 40 controls the fuel supply unit 29 to supply fuelto the engine 16 while monitoring exhaust gases from the engine 16 withthe exhaust gas sensor 23 so that any undesirable exhaust emissions willbe minimized.

When the engine 16 is thus ignited and started, since the exhaust gassensor 23 has already been activated, the rotational speed N and thethrottle opening of the engine 16 have been controlled for better fuelignitability, and the exhaust gas purifying catalyst 24 has already beenactivated, any undesirable exhaust emissions can sufficiently bereduced.

The engine 16 is continuously cranked when the engine 16 is thus ignitedand started.

In controlling the engine controller 18 and the generator controller 20after being activated, the electric generation management device 21determines, as described above with respect to the STEP 17, whether thecombustion of fuel in the engine 16 has reached a fully combusted stateor not based on a signal issued from the full-combustion determiningunit 41.

Specifically, whether the combustion of fuel in the engine 16 hasreached a fully combusted state or not is determined by thefull-combustion determining unit 41 in a full-combustion decision modeshown in FIG. 11.

As shown in FIG. 11, the full-combustion determining unit 41 detects arotational speed N and an engine load L of the engine 16 respectivelywith the engine speed sensor 27 and the load detector 26 in a STEP 1,and then determines an engine load L_(C) at the detected rotationalspeed N when the engine 16 is cranked and an engine load L_(F) when fuelstarts being combusted in the engine 16, i.e., when fuel is in anignited state to start the engine 16, from a data table shown in FIG.12, in a STEP 2. The data table shown in FIG. 12 contains variousdifferent engine loads L_(C), L_(F) experimentally determined at variousrotational speeds N of the engine 16. At any of the rotational speeds Nof the engine 16, the corresponding engine load L_(F) when fuel is inthe ignited state in the engine 16 is larger than the correspondingengine load L_(C) when the engine 16 is cranked. When fuel in the engine16 is in the fully combusted state in which the fuel combustion isstable in the engine 16, the load on the engine 16 is smaller than theengine load L_(F) and larger than the engine load L_(C) at any of therotational speeds N.

After having detected the engine load L_(F) and the engine load L_(C),the full-combustion determining unit 41 determines whether the presentdetected engine load L is greater than the engine load L_(C) uponcranking by a predetermined value ΔL (see FIG. 12) or not in a STEP 3.If L≦L_(C) +ΔL, i.e., if the present engine load L is close to theengine load L_(C) upon cranking, then the full-combustion determiningunit 41 determines that the engine 16 is being cranked.

If L>L_(C) +ΔL, then full-combustion determining unit 41 determineswhether the engine load L is smaller than the engine load L_(F) uponstart of fuel combustion (upon fuel ignition) by the predetermined valueΔL or not in a STEP 4. If L≧L_(F) -ΔL, i.e., if the present engine loadL is close to the engine load L_(F) upon start of fuel combustion, thenthe full-combustion determining unit 41 determines that the fuelcombustion in the engine 16 is in an ignited state in which the fuelcombustion is unstable.

If L_(F) -ΔL<L<L_(C) +ΔL, then the fuel combustion in the engine 16 isbasically considered to be in a fully combusted state. However, when thefuel combustion in the engine 16 is in an ignited state, the engine loadL may temporarily be in the condition: L<L_(F) -ΔL because the fuelcombustion is unstable. Therefore, the full-combustion determining unit41 determines whether the engine load condition: L_(F) -ΔL<L<L_(C) +ΔLhas continued for a predetermined period of time or not in a STEP 5. Ifthe engine load condition: L_(F) -ΔL<L<L_(C) +ΔL has continued for thepredetermined period of time, then the full-combustion determining unit41 issues a signal indicating that the engine load condition: L_(F)-ΔL<L<L_(C) +ΔL has continued for the predetermined period of time tothe electric generation management device 21 in a step 6. If the engineload condition: L_(F) -ΔL<L<L_(C) +ΔL has not continued for thepredetermined period of time, then the full-combustion determining unit41 determines that the fuel combustion in the engine 16 is still in anignited state.

The full-combustion decision mode thus carried out as described abovewith reference to FIG. 11 allows the electric generation managementdevice 21 to determine reliably that the fuel combustion in the engine16 is in a fully combusted state.

When the electric generation management device 21 has determined thatthe fuel combustion in the engine 16 is in a fully combusted state afterthe start of the fuel combustion, the electric generation managementdevice 21 determines whether the generator 17 is switched from the motormode to the generator mode based on a response signal from the generatorcontroller 20 in a STEP 19 in FIG. 6. If not, the switching commandingunit 34 instructs the generator controller 20 to switch the generator 17from the motor mode to the generator mode in a STEP 20.

The switching control unit 45 of the generator controller 20 nowswitches the generator 17 from the motor mode to the generator mode in agenerator switching control mode shown in FIG. 13.

Specifically, as shown in FIG. 13, the switching control unit 45 detectsa present rotational speed N of the generator 17 with the engine speedsensor 27 in a STEP 1. Then, the switching control unit 45 determines,according to a given formula, a command value I_(OUT) M for a motorcurrent necessary to bring the present rotational speed N of thegenerator 17 into agreement with the target starting rotational speedN_(CR) given from the starting rotational speed setting unit 32a whenthe generator 17 operates as an electric motor, in a STEP 2. Similarly,the switching control unit 45 determines, according to a given formula,a command value I_(OUT) G for a generator current necessary to bring thepresent rotational speed N of the generator 17 into agreement with thepresently given target starting rotational speed N_(CR) when thegenerator 17 operates as a generator, in a STEP 3.

The switching control unit 45 compares the detected rotational speed Nand the target starting rotational speed N_(CR) in a STEP 4. IfN≧N_(CR), i.e., if the rotational speed N is slightly higher than thetarget starting rotational speed N_(CR), then the switching control unit45 outputs the command value I_(OUT) M determined in the STEP 2 to thegenerator energy supply controller 19 in a STEP 5. The generator energysupply controller 19 now adjusts the duty cycle of switching pulsesaccording to the command value I_(OUT) M for thereby reducing therotational speed of the generator 17 so as to be lower than the targetstarting rotational speed N_(CR).

If N<N_(CR) in the STEP 4 (YES), i.e., if the rotational speed N isslightly lower than the target starting rotational speed N_(CR), thenthe switching control unit 45 reduces a command value I_(OUT) M_(X),which is presently given to the generator energy supply controller 19 tooperate the generator 17 as an electric motor, stepwise by apredetermined value ΔI_(M) until the command value I_(OUT) M_(X) willfinally becomes "0" (I_(OUT) M_(X) ←I_(OUT) M_(X) -ΔI_(M)), and outputsthe new command value I_(OUT) M_(X) to the generator energy supplycontroller 19 in STEPs 6˜8. The generator energy supply controller 19gradually reduces the amount of electric energy which is being suppliedfrom the battery 3 to the generator 17 to operate the generator 17 as anelectric motor.

Thereafter, the switching control unit 45 increases a command valueI_(OUT) G_(X), which is given to operate the generator 17 as agenerator, stepwise from an initial value I_(OUT) G_(INT) by apredetermined value ΔI_(G) until the command value I_(OUT) G_(X) willfinally reach the command value I_(OUT) G determined in the STEP 3(I_(OUT) G_(X) ←I_(OUT) G_(X) +ΔI_(G)), and outputs the new commandvalue I_(OUT) G_(X) to the generator energy supply controller 19 inSTEPs 9˜13. The generator energy supply controller 19 graduallyincreases the amount of electric energy generated by the generator 17,which has started to generate electric energy.

In the above generator switching control mode, the current command valueapplied to the generator energy supply controller 19 varies as shown inFIG. 14(a). At this time, the load imposed on the engine 16 by thegenerator 17 does not sharply vary, but gradually varies from acondition in which the engine 16 is actuated by the generator 17operating as an electric motor to a condition in which the engine 16actuates the generator 17 to cause the generator 17 to generate electricenergy, as shown in FIG. 14(b). Therefore, because the load on theengine 16 is not subject to sharp changes upon switching from the formercondition to the latter condition, the engine 16 operates stably anddoes not produce unwanted vibrations. Since the engine 16 operatesstably, the fuel combustion in the engine 16 is prevented from becomingunstable, and the engine 16 is prevented from emitting undesirable toxicexhaust gases.

After the generator switching control mode, the electric generationmanagement device 21 carries out a warm-up control mode for warming upthe engine 16 and generating electric energy with the generator 17 in aSTEP 21 in FIG. 6.

In the warm-up control mode, the electric generation control unit 36 ofthe electric generation management device 21 operates in an operationsequence shown in FIG. 15.

As shown in FIG. 15, the target rotational speed setting unit 36b andthe target generated output setting unit 36a of the electric generationcontrol unit 36 first determine, in a STEP 1, a target warm-uprotational speed N_(W) for the engine 16 and a target generated outputP_(W) for the generator 17, respectively, from respective data tablesshown in FIGS. 16 and 17 based on the temperature T_(W) of the engine 16which is presently detected by the temperature sensor 25.

The data tables shown in FIGS. 16 and 17 are established in order tosuppress unwanted exhaust emissions from the engine 16 and increase thegeneration efficiency of the generator 17 as much as possible.

Then, the electric generation control unit 36 determines, in a STEP 2, atarget reference current I_(UVW) for the generator 17 and a targetreference throttle opening TH_(BASE) for the engine 16 frompredetermined maps based on the target warm-up rotational speed N_(W)and the target generated output P_(W) which have been determined in theSTEP 1. The electric generation control unit 36 determines a commandvalue TH_(OUT) for the throttle opening of the engine 16 from the targetreference throttle opening TH_(BASE) according to a predeterminedformula in a STEP 3.

The command value TH_(OUT) for the throttle opening has been correcteddepending on the difference between the present rotational speed N ofthe engine 16 (=the rotational speed of the generator 17) and the targetwarm-up rotational speed N_(W) and the difference between the presentgenerated output of the generator 17 and the target generated outputP_(W), and is determined in order to equalize those differences to "0".

The electric generation control unit 36 outputs the determined throttleopening command value TH_(OUT) to the engine controller 18 in a STEP 4.The engine controller 18 now controls the throttle control unit 43 tocontrol the throttle opening of the engine 16 through the throttleactuator 28 according to the given command value TH_(OUT).

The electric generation control unit 36 then outputs target warm-uprotational speed N_(W), the target generated output P_(W), and thetarget reference current I_(UVW) to the generator controller 20 in aSTEP 5. The generator control unit 46 of the generator controller 20corrects the target reference current I_(UVW) depending on thedifference between the present rotational speed N of the generator 17and the target warm-up rotational speed N_(W) and the difference betweenthe present generated output of the generator 17 and the targetgenerated output P_(W) according to a predetermined formula, thereby todetermine a command value I_(OUT) for the generator current forequalizing the rotational speed of the generator 17 and the generatedelectric energy from the generator 17 to respective target values, andoutputs the command value I_(OUT) to the generator energy supplycontroller 19. The generator energy supply controller 19 adjusts theduty cycle of switching pulses according to the given command valueI_(OUT), thereby controlling the amount of electric energy generated bythe generator 17.

In the warm-up control mode, the rotational speed N of the engine 16 andthe generator 17 is controlled so as to be equal to the target warm-uprotational speed N_(W), and the generated output of the generator 17 iscontrolled so as to be equal to the target generated output P_(W). Theengine 10 is thus warmed up with low unwanted exhaust emissions, and thegenerator 17 is actuated by the engine 16 to generate electric energy.The electric energy generated by the generator 17 is supplied to thebattery 3 to charge the battery 3 and also to the propulsive electricmotor 4 to propel the hybrid vehicle.

In the warm-up control mode, the combustion control unit 42 of theengine controller 18 supplies fuel to the engine 16 to warm-up theengine 16 in a manner to reduce unwanted exhaust emissions whilemonitoring exhaust gases with the exhaust gas sensor 23.

When the propulsive electric motor 4 is subjected to regenerativebraking in the warm-up control mode, the regeneration control unit 37 ofthe electric generation management device 21 carries out a regenerationcontrol mode which corrects the throttle opening command value TH_(OUT)that is determined from time to time by the electric generation controlunit 36, in a STEP 25 shown in FIG. 6. Such a regeneration control modewill be described later on.

In the warm-up control mode, the outputting of the command value I_(OUT)for the generator current from the generator controller 20 to thegenerator energy supply controller 19 is delayed from the outputting ofthe throttle opening command value TH_(OUT) from the electric generationmanagement device 21 to the engine controller 18. Such output delayingwill also be described later on.

In FIG. 6, if the generator 17 switches its operation mode in the STEP19 and the engine 10 starts being warmed up, then the electricgeneration management device 21 determines, from time to time, whetherthe warming-up of the engine 16 is finished or not, for example, basedon the engine temperature T_(W) detected by the temperature sensor 25,in a STEP 22.

If the warming-up of the engine 16 is finished, the electric generationmanagement device 21 sets the E.M.Flg to "1" in a STEP 23, and carriesout an electric generation control mode in a STEP 24.

The electric generation control mode is carried out by the electricgeneration control unit 36 of the electric generation management device21 as shown in FIG. 18.

In FIG. 18, the target rotational speed setting unit 36b and the targetgenerated output setting unit 36a of the electric generation controlunit 36 determine a target reference rotational speed N_(BASE) for theengine 16 and the generator 17 and a target reference generated outputP_(BASE) for the generator 17, respectively, from respectivepredetermined data tables shown in FIGS. 19 and 20 based on the vehiclespeed V_(CAR) supplied from the vehicle speed sensor 9 through thevehicle propulsion management device 6, in a STEP 1. The data tablesshown in FIGS. 19 and 20 are determined such that as the vehicle speedV_(CAR) is higher, i.e., as the amount of electric energy required bythe propulsive electric motor 4 is greater, the amount of electricenergy generated by the generator 17 is greater. The data table oftarget reference rotational speeds N_(BASE) shown in FIG. 19 isdetermined as providing a rotational speed of the engine 16 forproducing an engine power output required to generate a target referencegenerated output P_(BASE) determined depending on the vehicle speedV_(CAR) and reducing unwanted exhaust emissions.

The target rotational speed setting unit 36b and the target generatedoutput setting unit 36a then correct the target reference rotationalspeed N_(BASE) depending on the difference with the present rotationalspeed N, thereby determining a target rotational speed N_(TR) for theengine 16 and the generator 17, and also corrects the target referencegenerated output P_(BASE) depending on the difference with the presentgenerated output, thereby determining a target generated output P_(TR),in a STEP 2.

The electric generation control unit 36 checks if the target rotationalspeed N_(TR) and the target generated output P_(TR) fall respectively inan allowable speed range of the engine 16 and the generator 17 and anallowable generated output range of the generator 17 in a STEP 3.Thereafter, the electric generation control unit 36 determines a targetreference current I_(UVW) for the generator 17 and a target referencethrottle opening TH_(BASE) for the engine 16 from predetermined maps inthe same manner as with the warm-up control mode, in a STEP 4.

Then, as with the warm-up control mode, the electric generation controlunit 36 corrects the target reference throttle opening TH_(BASE)according to a predetermined formula depending on the difference betweenthe target rotational speed N_(TR) and the present rotational speed Nand the difference between the target generated output P_(TR) and thepresent generated output, thus determining a command value TH_(OUT) forthe throttle opening which will equalize the rotational speed and thegenerated output to respective target values, in a STEP 5. The electricgeneration control unit 36 then outputs the command value TH_(OUT) tothe engine controller 18 in a STEP 6. The engine controller 18 nowcontrols the throttle control unit 43 to control the throttle opening ofthe engine 16 through the throttle actuator 28 according to the givencommand value TH_(OUT).

The electric generation control unit 36 outputs the target rotationalspeed N_(TR), the target generated output P_(TR), and the targetreference current I_(UVW) to the generator controller 20 in a STEP 7.The generator control unit 46 of the generator controller 20 correctsthe target reference current I_(UVW) depending on the difference betweenthe target rotational speed N_(TR) and the present rotational speed Nand the difference between the target generated output P_(TR) and thepresent generated output according to a predetermined formula, therebyto determine a command value I_(OUT) for the generator current. Theelectric generation control unit 36 controls the generator energy supplycontroller 19 to control the amount of electric energy generated by thegenerator 17 according to the given command value I_(OUT).

In the electric energy generation mode, the rotational speed N of theengine 16 and the generator 17 is controlled so as to be equal to thetarget rotational speed N_(TR), and the generated output of thegenerator 17 is controlled so as to be equal to the target generatedoutput P_(TR). The generation of electric energy is thus effectedadequately by the generator 17 depending on conditions in which thehybrid vehicle operates. The electric energy generated by the generator17 is supplied to the battery 3 to charge the battery 3 and also to thepropulsive electric motor 4 to propel the hybrid vehicle. Since theamount of electric energy generated by the generator 17 is greater asthe amount of electric energy required by the propulsive electric motor4 is greater, the amount of electric energy supplied from the battery 3to the propulsive electric motor 4 may be smaller when the amount ofelectric energy required by the propulsive electric motor 4 is greater,and any reduction in the capacity of the battery 3 is minimized.

In the electric energy generation mode, the combustion control unit 42of the engine controller 18 supplies fuel to the engine 16 to warm upthe engine 16 in a manner to reduce unwanted exhaust emissions whilemonitoring exhaust gases with the exhaust gas sensor 23.

When the propulsive electric motor 4 is subjected to, or is beingsubjected to, regenerative braking in the electric energy generationmode or the warm-up control mode, the regeneration control unit 37 ofthe electric generation management device 21 carries out a regenerationcontrol mode which corrects the throttle opening command value TH_(OUT)that is determined by the electric generation control unit 36 of theelectric generation management device 21.

The regeneration control mode is carried out as shown in FIG. 21. InFIG. 21, while electric energy is being generated by the generator 17,the regeneration control unit 37 determines from time to time whetherthe motor current I_(M) supplied from the current sensor 10b through thevehicle propulsion management device 6 is a current flowing from thebattery 3 to the propulsive electric motor 4 or a regenerated currentflowing from the propulsive electric motor 4 to the battery 3, based onthe direction of the motor current I_(M) in a STEP 1.

If the motor current I_(M) is not a regenerated current, i.e., if thepropulsive electric motor 4 has not yet been subjected to regenerativebraking, then the regeneration control unit 37 determines whether thehybrid vehicle has been braked or not based on a braking signal from thebrake switch 8 in a STEP 2 and also determines whether a reduction withtime in the accelerator operation A from the accelerator operationsensor 7 has exceeded a predetermined value or not in a STEP 3.

If the hybrid vehicle has been braked or the accelerator operation A hasbeen reduced relatively greatly, then since regenerative braking isabout to be effected on the regenerative electric motor 4, theregeneration control unit 37 determines a corrective value ΔTH for thethrottle opening command value TH_(OUT) as a predetermined value ΔTH_(O)in a STEP 4. The regeneration control unit 37 then subtracts thedetermined corrective value ΔTH from the throttle opening command valueTH_(OUT) which is determined by the electric generation control unit 36as described above, thereby correcting the throttle opening commandvalue TH_(OUT) in a STEP 5. The electric generation control unit 36outputs the corrected command value TH_(OUT) to the engine controller81.

If the motor current I_(M) is a regenerated current in the STEP 1 (YES),i.e., if the propulsive electric motor 4 has already been subjected toregenerative braking, then the regeneration control unit 37 determinesan amount of regenerated electric energy according to a predeterminedformula from the regenerated current I_(M) and a voltage V_(B) detectedby the voltage sensor 11 in a STEP 6. Based on the magnitude of thedetermined amount of regenerated electric energy, the regenerationcontrol unit 37 determines a corrective value ΔTH for the throttleopening command value TH_(OUT) from a predetermined data table shown inFIG. 22 in a STEP 7. Basically, the corrective value ΔTH is greater asthe amount of regenerated electric energy is greater.

Thereafter, the regeneration control unit 37 subtracts the determinedcorrective value ΔTH from the throttle opening command value TH_(OUT)which is determined by the electric generation control unit 36 asdescribed above, thereby correcting the throttle opening command valueTH_(OUT) in the STEP 5.

The throttle opening command value TH_(OUT) is corrected for thefollowing reasons: When the propulsive electric motor 4 is operating asan electric motor, the electric load on the generator 17 is imposed byboth the battery 3 and the propulsive electric motor 4. When thepropulsive electric motor 4 is subjected to regenerative braking, noelectric energy is supplied to the propulsive electric motor 4, and theelectric load on the generator 17 is imposed by only the battery 3, andhence is greatly reduced. When the electric load on the generator 17 isgreatly reduced, the load on the engine 16 which actuates the generator17 is also greatly reduced. Consequently, the engine 16 tends to raceeasily. When the engine 16 races, the engine 16 discharges undesirableexhaust emissions and unduly vibrates. This condition can be avoided bycorrecting the throttle opening in a manner to decrease (in a closingdirection) when regenerative braking is about to be effected or beingeffected on the propulsive electric motor 4.

In the electric energy generation mode or the warm-up control mode, thegenerator current command value I_(OUT) which is determined from time totime by the generator controller 20 under the command of the electricgeneration control unit 36 is outputted to the generator energy supplycontroller 19 at a time slightly after the time at which the throttleopening command value TH_(OUT) (which may be corrected by theregeneration control unit 37) determined from time to time by theelectric generation control unit 36 concurrent with the calculation ofthe generator current command value I_(OUT) is outputted to the enginecontroller 18.

More specifically, as shown in FIG. 23, in the electric generationcontrol mode, for example, the electric generation control unit 36 andthe generator control unit 46 simultaneously determine a command valueTH_(OUT) for the throttle opening and a command value I_(OUT) G for thegenerator current, respectively, as described above in a STEP 1, andthereafter the rotational speed change calculating unit 36c determines adifference ΔN_(TR) between the target rotational speed N_(TR)(corresponding to the present rotational speed of the engine 16 and thegenerator 17) for the generator 17 which has been given to the generatorcontroller 20 in a preceding cycle time and the target rotational speedN_(TR) for the generator 17 which has been given to the generatorcontroller 20 in a present cycle time in a STEP 2.

The rotational speed increase/decrease determining unit 36d determineswhether the rotational speed of the engine 16 is increased or reduceddepending on whether the difference ΔN_(TR) is positive or negative in aSTEP 3. If ΔN_(TR) >0, then the electric generation management device 21determines a delay time T_(DLY) for the time to output the generatorcurrent command value I_(OUT) G from a predetermined speed increasingmap based on the present rotational speed N detected by the engine speedsensor 27 and the difference ΔN_(TR) in a STEP 4a. If ΔN_(TR) <0, thenthe electric generation management device 21 determines a delay timeT_(DLY) for the time to output the generator current command valueI_(OUT) G from a predetermined speed reducing map based on the presentrotational speed N and the difference ΔN_(TR) in a STEP 4b.

The speed increasing map and the speed reducing map are representativeof delay times T_(DLY) experimentally determined after the throttleopening command value TH_(OUT) has been outputted to the enginecontroller 18 until the power output of the engine 16 reaches a poweroutput corresponding to the target generated output P_(TR) for thegenerator 17, respectively when the rotational speed N of the engine 16increases and decreases, with the rotational speed N of the engine 16and the difference ΔN_(TR) as parameters, i.e., are representative ofthe correlation between the rotational speed N, the difference ΔN_(TR),and the delay time T_(DLY). Basically, the delay time T_(DLY) decreasesas the rotational speed N is higher and increases as the differenceΔN_(TR) is greater. The delay time T_(DLY) is shorter when therotational speed N of the engine 16 increases than when the rotationalspeed N of the engine 16 decreases. The delay time T_(DLY) is determinedby the delay time estimating unit 36e of the electric generation controlunit 36.

Then, the electric generation management device 21 outputs the throttleopening command value TH_(OUT) from the electric generation control unit36 to the engine controller 18, varying the throttle opening of theengine 16 in a STEP 5. The electric generation management device 21determines whether the delay time T_(DLY) has elapsed or not in a STEP6. If the delay time T_(DLY) has elapsed, then the electric generationmanagement device 21 controls the generator controller 20 to output thegenerator current command value I_(OUT) G to the generator energy supplycontroller 19, varying the duty cycle of switching pulses which controlthe amount of electric energy generated by the generator 17 to equalizethe generated output of the generator 17 to the target generated outputP_(TR) in a STEP 7.

The above operation sequence shown in FIG. 23 is carried out also in thewarm-up control mode.

The time to output the generator current command value I_(OUT) G isdelayed for the reasons described below.

When the generator current command value I_(OUT) G is given to thegenerator energy supply controller 19, the generated output of thegenerator 17 is immediately electrically controlled into agreement withthe target generated output P_(TR). However, when the throttle openingcommand value TH_(OUT) is given to the engine controller 18, thethrottle opening is mechanically varied by the throttle actuator 28according to the throttle opening command value TH_(OUT), but the amountof intake air supplied to the engine 16 is not immediately equalized toan amount corresponding to the varied throttle opening. A certain timeis required after the throttle opening command value TH_(OUT) is givento the engine controller 18 until the power output of the engine 16reaches a power output that corresponds to the target generated outputP_(TR) for the generator 17. Such a certain time differs depending onthe rotational speed of the engine 16 and a change in the rotationalspeed of the engine 16 due to a change in the throttle opening commandvalue TH_(OUT), and also differs depending on whether the rotationalspeed of the engine 16 increases or decreases due to a change in thethrottle opening command value TH_(OUT).

To avoid the above problems, the time to output the generator currentcommand value I_(OUT) G is delayed for the delay time T_(DLY) dependingon the target rotational speed N_(TR) for the engine 16, the differenceΔN_(TR), and whether the difference ΔN_(TR) is positive or negative,i.e., whether the rotational speed is increased or reduced. When thetime to output the generator current command value I_(OUT) G is delayedfor the delay time T_(DLY), the power output of the engine 16 is causedto match the generated output of the generator 17 at the time thegenerated output of the generator 17 is controlled into agreement withthe target generated output P_(TR) according to the generator currentcommand value I_(OUT) G. The electric control of the generated output ofthe generator 17 and the mechanical control of the power output of theengine 16 (the drive forces for the generator 17) are now synchronizedwith each other, and the load on the engine 16 matches its power outputwhen the generator 17 generates electric energy. Therefore, no undueload is imposed on the engine 16, and the engine 16 operates stably. Asa consequence, the engine 16 is prevented from discharging undesirableexhaust emissions and unduly vibrating.

On the hybrid vehicle in the above embodiment, the above operationsequence is repeated in each of the cycle times. Specifically, if theremaining capacity C of the battery 3 is reduced (C<C_(L)) or thebattery 3 is unable to output the amount of electric energy required topropel the hybrid vehicle (P_(MAX) ≦P_(motor)) while the vehiclepropelling apparatus 1 is in operation such as when the hybrid vehicleis running, then except when the canister is being purged, the engine 16is started by the generator 17 acting as a starter motor. After theengine 16 has been warmed up, the generator 17 generates electric energydepending on conditions in which the hybrid vehicle runs, and thegenerated electric energy is supplied to the battery 3 and thepropulsive electric motor 4.

When the hybrid vehicle is running on a highland, for example, since airsupplied to the engine 16 for burning fuel therein is thinner than inplain geographical regions, drive forces produced by the engine 16 aresmaller than in plain geographical regions, and hence the amount ofelectric energy generated by the generator 17 is reduced, allowing thebattery 3 to be discharged quickly. However, inasmuch as the thresholdvalue C_(L) for determining the time to activate the electric energygenerating apparatus 2 is greater as the atmospheric pressure is lower,the battery 3 and the propulsive electric motor 4 start being suppliedwith electric energy from the generator 17 at an early stage where thecapacity of the battery 3 is relatively large. Therefore, since it takestime until the capacity of the battery 3 is lowered to a level where thebattery 3 needs to be charged, the hybrid vehicle can travel in asufficiently long range on the highland in the same manner as when itruns in plain geographical regions.

When the battery 3 is unable to output the amount of electric energyrequired to propel the hybrid vehicle (P_(MAX) ≦P_(motor)), the electricenergy generating apparatus 2 begins to generate electric energy.Consequently, the running performance of the hybrid vehicle issufficiently maintained.

As described above, the electric energy generating apparatus 2 isactivated at an appropriate time determined in view of the condition ofthe battery 3 and the running performance of the hybrid vehicle, forsupplying electric energy to the battery 3 and the propulsive electricmotor 4. When the engine 16 is started, it tends to produce unwantedexhaust emissions and undue vibrations. However, because the engine 16is started under adequate conditions as described above, the engine 16has exhaust gas properties and vibration characteristics optimized forenvironmental protection.

While the electric energy generating apparatus 2 is activated dependingon the remaining capacity C of the battery 3 and the effective maximumoutput P_(MAX) in the above embodiment, the electric energy generatingapparatus 2 may be activated only when the rate of change with time ofthe remaining capacity C sharply decreases beyond a given value due to asharp increase in the accelerator operation A. Specifically, when theremaining capacity C of the battery 3 is of a relatively low level, ifthe accelerator operation A is sharply increased, then the remainingcapacity C of the battery 3 is sharply reduced, and no sufficientelectric energy is supplied from the battery 3 to the propulsiveelectric motor 4, with the result that the hybrid vehicle may not beable to meet certain required demands for running performance, e.g., maynot be able to accelerate quickly. In such a case, the electric energygenerating apparatus 2 may be activated to avoid the above shortcoming.

While the starting rotational speed N_(CR) of the engine 16 isestablished depending on the engine temperature T_(W) in the aboveembodiment, the starting rotational speed N_(CR) may be establisheddepending on the intake temperature of the engine 16.

Although a certain preferred embodiment of the present invention hasbeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

What is claimed is:
 1. An electric generation control system for use ona hybrid vehicle having a vehicle propelling apparatus including abattery and a propulsive electric motor energizable by the battery, andan electric energy generating apparatus including an engine and agenerator actuatable by the engine, the generator being operable in agenerator mode in which the generator is actuated by the engine togenerate electric energy to be supplied to the battery and/or thepropulsive electric motor while the vehicle propelling apparatus is inoperation, said electric generation control system comprising:targetgenerated output setting means for establishing a target generatedoutput for the generator depending on an operating condition of thehybrid vehicle; intake air control valve control means for controllingthe opening of an intake air control valve of the engine to enable theengine to produce a power output corresponding to said target generatedoutput; generator control means for varying the electric energygenerated by the generator to equalize the generated electric energy tosaid target generated output; and delay time estimating means forestimating a delay time until the engine produces the power outputcorresponding to said target generated output after the opening of theintake air control valve starts being varied by said intake air controlvalve control means depending on a change in said target generatedoutput, according to a preset correlation between delay times androtational speeds of the engine based on a present rotational speed ofthe engine; said generator control means comprising means forcontrolling the electric energy generated by the generator based on saidtarget generated output upon elapse of said delay time after the openingof the intake air control valve starts being varied by said intake aircontrol valve control means.
 2. An electric generation control systemaccording to claim 1, wherein said target generated output setting meanscomprises means for establishing the target generated output for thegenerator depending on at least a vehicle speed of the hybrid vehicle.3. An electric generation control system according to claim 1, furthercomprising means for warming up the engine while causing said generatorto generate electric energy depending on a temperature of the engineimmediately after the engine and the generator have been started, saidtarget generated output setting means comprising means for establishingthe target generated output depending on the temperature of the enginewhen the engine is warmed up.
 4. An electric generation control systemaccording to claim 3, wherein said target generated output setting meanscomprises means for establishing the target generated output for thegenerator depending on at least a vehicle speed of the hybrid vehicleafter the engine has been warmed up.
 5. An electric generation controlsystem according to claim 1, wherein said intake air control valvecontrol means for determining a target rotational speed for the engineto produce a power output from the engine corresponding to said targetgenerated output, and controlling the opening of the intake air controlvalve to equalize the rotational speed of the engine to said targetrotational speed.
 6. An electric generation control system according toclaim 1, further comprising rotational speed change calculating meansfor determining a change in the rotational speed of the engine dependingon a change in said target generated output, said delay time estimatingmeans comprising means for estimating the delay time according to apreset correlation between delay times, rotational speeds of the engine,and changes in the rotational speed based on the present rotationalspeed of the engine and the determined change in the rotational speed.7. An electric generation control system according to claim 6, whereinsaid correlation is arranged such that the delay time is shorter as therotational speed of the engine is higher and longer as the change in therotational speed of the engine is larger.
 8. An electric generationcontrol system according to claim 6, further comprising rotational speedincrease/decrease determining means for determining whether therotational speed of the engine increases or decreases depending on thechange in the target rotational speed, said correlation being availableseparately when the rotational speed of the engine increases and whenthe rotational speed of the engine decreases.
 9. An electric generationcontrol system according to claim 8, wherein said correlation which isavailable separately when the rotational speed of the engine increasesand when the rotational speed of the engine decreases is arranged suchthat said delay time is shorter when the rotational speed of the engineincreases than when the rotational speed of the engine decreases.